The Humane Society and other animal advocates have criticised pet cloning as potentially dangerous to the animals involved and wasteful, given the millions of dogs and cats that are destroyed each year in US animal shelters.

Sperling, an Arizona entrepreneur who launched the for-profit University of Phoenix, underwrote the cloning of the first cat, CC, for Carbon Copy, who was born in 2001.

Genetic Savings & Clone runs a pet bank service allowing pet owners to send in a tissue sample for later cloning. The company says it expects to offer dog cloning in 2005. Sperling founded the company as part of a bid to clone his dog, Missy.

Dolly, a sheep cloned by Scottish researchers in 1996, was the first mammal to be cloned from an adult cell.